Torsional Strengthening of Rectangular RC Beam using Stainless Steel Wire Mesh (SSWM)

Abstract

The existence of torsion considerably changes the failure mode of Reinforced Concrete (RC) members. The issue of upgrading the existing civil engineering infrastructure has been of great importance for over a decade. The bridge deck, beam, girders columns, buildings, parking structures, and other structures are deteriorating due to aging environmental induced deterioration, poor initial design or construction, or lack of maintenance, as well as accidental events such as earthquakes, tsunamis, and other natural disasters. Therefore, infrastructure increasing the decaying in frequency combining the need for the up-gradation so that the structure can meet the more stringent design requirements. Hence, aspects of civil engineering infrastructure strengthened have received considerable attention over the past few years throughout the world. FIB and CNR-DT are currently the only guidelines applicable to the design of Fiber Reinforced Polymer (FRP) composites for torsional strengthening in the world. But so far there are no such guidelines are readily available in our country even for FRP and SSWM. So the results of this study will be useful to develop the guideline for the torsional strengthening of RC element using SSWM. The results of this study will also help to develop the application process of SSWM as a strengthening material on RC elements for the concrete construction industry. Locally available stainless steel wire mesh (SSWM) is a strong durable costefficient and corrosion-resistant material, so the performance of SSWM in the torsional strengthening of the RC specimen is explored in this study. An analytical model based on the softened membrane model for torsion (SMMT) modified for SSWM strengthened beams and numerical simulation are performed to investigate the torsional behaviour of RC beams under different wrapping configurations. A nonlinear finite element analysis based on concrete damage plasticity (CDP) and tension stiffening relationship of concrete is accompanied using commercial software ABAQUS. Similarly, an analytical study is carried out in MATLAB by using the Softened Membrane Model for Torsion with SSWM (SMMT-SSWM). The model is validated by comparing the analytical and FEA response of the four rectangular RC beams strengthened with FRCM composites. The model is also able to predict the damage pattern, ultimate torsional moment, and the corresponding angle of twist per unit length with reasonable accuracy with the experiment results. Based on the investigations presented in this study, it is observed that reinforced concrete beams wrapped in various configurations of SSWM wrapping exhibited a considerable rise in cracking and ultimate twisting moment compared to the control specimens. An experimental investigation is conducted on the rectangular RC beams strengthened with SSWM. A total of 8 beams with M25 grade of concrete are prepared. The experimental investigation comprises of testing eight rectangular RC beams with a cross-section of 100 mm × 225 mm and length 1300 mm. The beams are reinforced with 4-10 mm diameter longitudinal bars and 2 leg-8 mm diameter stirrups at 150 mm c/c. Two beams without SSWM strengthening are used as control specimens and six beams are externally strengthened by three different SSWM wrapping configurations. SSWM wrapping configurations considered for beams under pure torsion are Rectangular CONtrol specimen (RCON), Rectangular beam with Corner and 100 mm Strip In between Stirrups (RCO&100SIS), Rectangular beam with Corner and Diagonal Strip wrapping (RCO&DS), and Rectangular beam with Full Wrapping (RFW). To investigate the effectiveness of strengthening by Stainless Still Wire Mesh (SSWM) and to find out a better alternative for torsional strengthening, an experimental study is conducted. The results indicates that the SMMT model can accurately predict the torsional response of fully wrapped reinforced beams with fiber rupture failure mode. The Rectangular beams strengthened with COrner and Diagonal Strip wrapping (RCO&DS) configuration exhibited better improvement in torsional capacity compared to other wrapping configurations.